Defense Agents Research Articles

Geranium defensive agents. IV. Chemical and morphological bases of resistance

Insect-resistant and -susceptible geranium plants (Pelargonium xhortorum) were chemically and morphologically compared to assess the relative importance of resistance components. Glandular and nonglandular trichome density and quantification of trichome exudate (anacardic acids) from inbred resistant and susceptible lines were determined. Three different extraction procedures were employed to quantify the anacardic acids: (1) capillary solvent extract, (2) leaf wipe, and (3) whole leaf extract. The results support the conclusion that tall glandular trichomes and the exudate they produce are the most important factors in small pest resistance in the geranium. In addition, it was shown that tall glandular trichome densities are less and the ability of the plant to express the anacardic acids as exudate on the trichome head exterior is lacking in the susceptible lines analyzed, even though all lines possessed the capability to synthesize the anacardic acids. A plant line of intermediate resistance character was shown to possess high densities of tall glandular trichomes but resembled susceptible plants in lacking the ability to express the anacardic acids as an exudate in appreciable quantities.

Geranium defensive agents. III. Structural determination and biosynthetic considerations of anacardic acids of geranium

Ozonolysis, dithioether derivatization, and EI and CI mass spectrometry were used to establish the location of the double bond in the side chain of the two major anacardic acids in geranium (Pelargonium hortorum) trichome exudate. The point of unsaturation was shown to be between C-5 and C-6 counting from the methyl end of the side chain, contradicting the earlier hypothesis that the olefmic bond was probably at the 9-10 position based upon expected biosynthetic considerations. The two major components are thus 6-[(Z)-10'-pentadecenyl]salicylic acid (C22H34O3) and 6-[(Z)-12'-heptadecenyl] salicylic acid (C24H38O3). This may indicate that the precursor of these anacardic acids is a saturated fatty acid since the location of a double bond at the 5-6 position is unusual among the unsaturated fatty acids. Capillary GLC and HPLC of the trichome exudate indicated the presence of small amounts of other anacardic acid analogs possessing such features as odd numbers of carbon atoms and saturated side chains.

Thiophenes and benzofurans in the undisturbed rhizosphere ofTagetes patula L.

Marigold (Tagetes patula L.) contains secondary metabolites toxic to various organisms. While these compounds may function as defensive agents in the plant, it is not clear whether they are exuded into the rhizosphere. Using a continuous root exudate trapping system and capillary column gas chromatography/mass spectrometry/data system, four thiophenes and two benzofurans were identified in the root exudates collected from the undisturbed rhizosphere of marigold. The importance of rhizospheric chemistry in the study of allelopathy is stressed.

Extracellular localization of pokeweed antiviral protein.

Pokeweed antiviral protein is an enzyme of Mr 29,000 known to inactivate a wide variety of eukaryotic ribosomes. We have used electron microscopy to show that the antibody specific for the protein is bound within the cell wall matrix of leaf mesophyll cells from Phytolacca americana. Any penetration or breakage of the cell wall and membrane could allow the enzyme to enter the cytoplasm, where it is likely to inhibit protein synthesis in the damaged cell. We speculate that pokeweed antiviral protein is a defensive agent whose principal function is probably antiviral.

Tetrodotoxin as a biological defense agent for puffers.

The skin of toxic puffers (Fugu niphobles, F. vermicularis vermicularis and F. pardalis) was found to release 5-80MU of tetrodotoxin (TTX) per specimen when lightly stimulated by handling. The puffer did not release any more toxin when the handling stimuli were repeated 3-5 times at a 30 min-interval. Some of them, however, recovered to release TTX on handling stimulus when kept intact for two weeks. The cultured puffer (F. rubripes rubripes) specimens which were artificially toxified by feeding with toxic puffer livers, released TTX up to 540 MU on a single handling stimulus.From these and other results, it was strongly suggested that TTX acts as a biological defense agent in puffers.

Oxidants from phagocytes: agents of defense and destruction

Oxidants from phagocytes: agents of defense and destruction

Oxidants From Phagocytes: Agents of Defense and Destruction

Oxidants From Phagocytes: Agents of Defense and Destruction

Defense of Ripe Fruit from Pests: Its Significance in Relation to Plant-Disperser Interactions

Ripe fruits of vertebrate-dispersed plants are susceptible to irreversible damage by pathogens and invertebrates while they are attached to the parent plant "waiting" for the visit of a dispersal agent. Adaptations of plants to decreasing fruit damage include temporal escape from pests, reducing exposure time, and decreasing fruit profitability to pests by means of secondary compounds and reduced and/or unbalanced nutrient content. A variety of secondary compounds has been reported from the ripe fruits of many vertebrate-dispersed plants, including alkaloids, saponins, volatile oils, resins and phenolics. Toxic fruits containing poisonous substances that potentially are defensive agents against pests may be very frequent, as revealed by an analysis of their occurrence among European plants. As judged from the literature, fruits containing secondary substances are at a competitive disadvantage relative to nontoxic ones. It is suggested that a hierarchy of fruit defense methods should exist, with the least desirable ones selected for only when better mechanisms are precluded or rendered ineffective. A simplified model is proposed to explain the occurrence of toxic mature fruits; the roles of pest pressure and plant competition for disperser services are considered, and some testable predictions are suggested. It is finally argued that nutritionally unbalanced fruits or those with secondary compounds probably serve indirectly as a means of increasing the potential for plant coexistence through their diversifying effects on diet selection by individual frugivores.

Identification of leukin in amniotic fluid

SummaryLeukin, a cationic bactericidal protein of low molecular weight that is derived primarily from the polymorphonuclear leucocyte, was found to be present in amniotic fluid from 450 normal obstetric patients at teim. The concentration in the amniotic fluid was very similar to that found in circulating maternal plasma, probably indicating simple diffusion of leukin. Neutralisation of amniotic fluid leukin with specific antisera did not change the in vitro bactericidal activity of whole amniotic fluid. The role of leukin as a nonspecific host defence agent in amniotic fluid is thought to be minimal

Synthesis of the ladybug defensive agents (±)-hippodamine, (±)-convergine, (±)-hippocasine and (±)-hippocasine oxide

The total syntheses of the ladybug defensive agents (±)-hippodamine, (±)-convergine, (±)-hippocasine, and (±)-hippocasine oxide are described starting from perhydroboraphenalene.

Defensive secretions of three species ofAcilius (Coleoptera: Dytiscidae) and their seasonal variations as determined by high-pressure liquid chromatography

A rapid, sensitive, stable, and quantitative high-pressure liquid chromatographic technique was developed for the analysis of defensive secretions obtained from the pygidial and prothoracic glands of dytiscids. Methods were developed for both normal phase (μPorasil) and reverse phase (μBondapak C18) columns. The applicability of this technique was demonstrated when defensive compounds ofAcilius semiculcatus, A. sylvanus andA. mediatus were isolated, identified, and quantitated. No major differences were found in the composition of the defensive secretions between the three species. The seasonal defensive titer ofA. semisulcatus was determined from June through October 1977. The pygidial defensive agents (benzoic acid,p-hydroxybenzaldehyde, and methylp-hydroxybenzoate varied from 9.0 to 67.8 μg and exhibited a maximum in July, and a steroid from the prothoracic gland varied from 7.1 to 33.2 μg and was maximum in October.

Stereoselective total synthesis of the ladybug defensive agents coccinellin and precoccinellin

The stereoselective total synthesis of the lady bug defensive agents coccinellin and precoccinellin is described starting from perhydroboraphenalene.

Marine natural products revisited

Some of the most recent intriguing reports on the chemistry of marine natural products include work with saxitoxin, the paralytic shellfish poison with other toxin, and with chemical signal and defense agents.

Politics: The Defensive Agent Speaks

Politics: The Defensive Agent Speaks

Physico-Chemical Defense of Vertebrate Organisms: The Role of Bile Acids in Defense Against Bacterial Endotoxins

PHYSICO-CHEMICAL DEFENSE OF VERTEBRATE ORGANISMS: THE ROLE OF BILE ACIDS IN DEFENSE AGAINST BACTERIAL ENDOTOXINS LÓRÁND BERTÓK* The discovery of the causes of many infectious diseases and the resultant elaboration of more effective protection against them has produced the illusion in the minds of some researchers that it would only be a matter of time before the pathogenic agent of every infectious disease and the specific protection against it is fully worked out. Furthermore, the persistent search for new specific defense (active and passive immunization ) and antiinfectious (antibiotic) agents has resulted in the overshadowing of the investigation of natural, so-called nonspecific defense mechanisms. Over the years it has become obvious that there were some infectious agents against which the organism seemed incapable of developing sufficient specific immunologic defenses. A number of these infectious agents are gram negative bacteria. Sepsis and toxemia caused by some of these agents may be catastrophic despite the use of antibiotics . According to recent statistics, 300,000 persons in the United States have developed gram negative sepsis in hospitals, and approximately 100,000 of them have died annually [1, 2]. Dyspepsie colitis of neonates induced by Escherichia coli and perhaps other gram negative organisms may be an instructive disease within this general category. This enterotoxemia occurs quite frequently in newborn domestic animals (pig, calf) and more rarely in newborn humans; deaths of neonatal domestic animals as a result of this enterotoxic disorder are of considerable economic importance [3-7]. Despite the fact that these enterotoxemias have been known for many years, their pathogenesis is barely understood. The disorder is apparently due to several different gram negative intestinal organisms. Neither the classical immunologic methods (vaccination) nor antibiotic therapy has led to reliable means of prophylaxis or therapy. Since endotoxins derived from the bacterial cell wall have been recognized as the toxin responsible for ?Head, Department of Applied Radiation, Frédéric Joliot-Curie National Research Institute for Radiobiology and Radiohygiene, Budapest, Hungary. Supported in part by the Scientific Research Council, Ministry of Health, Hungary (6-13-1001-0/B). 70 I Lóránd Bertók ¦ Bile Acids in Defense the development of enterotoxemia, the question of natural, nonspecific resistance must be considered. On the basis of early work in our laboratory and recent reports drawn from the literature, the possible role of bile acids in the defense against the noxious influence of these bacterial endotoxins has finally been recognized. It has long been known that the toxic effects of bacterial endotoxins under experimental conditions can only be induced when they are administered parenterally [5, 8]. Although naturally occurring enterotoxemia results from absorption of the endotoxin from the intestinal tract, parenterally (intraperitoneal or intravenous) administered endotoxin causes prostration, diarrhea, and circulatory disturbances indistinguisable from those observed in the natural disease [5, 7, 9]. At autopsy animals killed by parenterally administered endotoxin which died in endotoxin shock show changes that are similar to the natural diseases (intestinal edema, hemorrhages) [9]. The experimental models differed from natural diseases only in the mode by which endotoxin entered the blood circulation. Thus the induction of"enteroxtoxemia" by parenteral endotoxin injection has served as a useful experimental model [10-12]. Our examinations have shown that there are phylogenetic correlations of endotoxin sensitivity [5]. Some species are more sensitive than others to administered endotoxin. Thus, man, horse, cattle, and guinea pigs demonstrate extreme sensitivity; birds are sensitive only in a certain embryonic stage, and amphibians and fishes are absolutely resistant [13]. The sensitivity appears to increase as one ascends the phylogenetic scale. Given orally, endotoxin is without effect in even the most sensitive species, when given in doses from 500 to 3,000 times the minimal parenterally lethal dosage. It is also ineffective when the intestinal mucosa of the experimental animal has been damaged by the injection of a histamine liberator or ionizing radiations [8]. There is no in vitro evidence for the existence of an intestinal enzyme which could specifically decompose the endotoxins and thus produce resistance to the orally administered material [14]. As a matter of fact orally administered endotoxin can be recovered essentially unaltered from the gastrointestinal tract by means of a phenol-water extraction...

Physiological activity of water beetle defensive agents. I. Toxicity and anesthetic activity of steroids and norsesquiterpenes administered in solution to the minnowPimephales promelas Raf.

By means of a bioassay employing the minnowPimephales promelas, the anesthetic activities and toxicities of various defensive steroids and norsesquiterpenes produced by the Dytiscidae and Gyrinidae were compared with those of a wide selection of steroid standards. The most widely occurring major components of dytiscid secretions, 4-pregnen-3-ones and related derivatives, were among those compounds most active in minnow bioassays. The norsesquiterpenes gyrinidal and gyrinidione were among the most toxic compounds tested but they possessed little anesthetic action. The anesthetic activity of gyrinidone was comparable to that of testosterone. Steroid activity in the minnow bioassay was highly related to the degree of oxygenation; steroids oxygenated only at the termini of the molecule were most active. Less or additional oxygenation resulted in a loss of activity. When steroids were rapidly administered to minnows the activities of many of them were similar, suggesting they share a common mode of action.

Physiological activity of water beetle defensive agents. II. Absorption of selected anesthetic steroids and norsesquiterpenes across gill membranes of the minnowPimephales promelas Raf.

The uptake of selected steroids and norsesquiterpenes by live minnows,Pimephales promelas, was studied when the compounds were administered externally in aqueous solution. The gills of minnows absorbed 80% of the steroid removed from solution. Steroid absorption across minnow gills is apparently a nonmediated process as rate saturation could not be demonstrated. Initial absorption rates of test compounds were inversely correlated with (1) the degree of oxygenation, (2) water solubility, and (3) polarity on silica gel thin-layer chromatography. These findings support the Stein model of non-mediated transport. The majority of compounds anesthetic and toxic to minnows exerted their effects at a similar internal concentration. Anesthesia occurred at ca. 10−6–10−5 M and death at 10−4–10−3 M. Since various agents causing membrane stabilization and lysis in in vitro systems act in an identical concentration range, it is proposed that the defensive steroids and norsesquiterpenes of water beetles act via membrane stabilization and lysis.

Defensive agents of the American water beetles Agabus seriatus and Graphoderus liberus

Electrical shocking and rapid temperature reduction induced the dytiscid beetles Agabus seriatus and Graphoderus liberus to excrete pygidial and prothoracic defensive substances. When minnows ( Pimephales promelas) were introduced into aqueous solutions of the defensive excretions from either beetle, they were rapidly inactivated and killed. The active agent was extractable in chloroform and constituted the major lipid component of the prothoracic defensive excretions. By means of thin-layer and gas-liquid chromatography, and ultraviolet and mass spectrometry, the biologically active material from the prothoracic defensive glands of both beetles was identified as a single steroid 11-deoxycorticosterone (DOC). The sensitivity of P. promelas to low levels of DOC made possible the development of a quantitative bioassay for this steroid in the defensive excretions. Quantitation by u.v. absorption at 240 nm and by the Pimephales bioassay showed A. seriatus contained ca. 40 μg DOC per beetle and G. liberus contained ca. 20 μg DOC per beetle. The major lipid component of the pygidial excretions of both beetles, p-hydroxybenzaldehyde, exhibited no toxic effect against test fish.

The antifungal factors in barley. V. Antifungal activity of the hordatines

The hordatines, antifungal substances previously isolated from barley seedlings grown in the dark, are also produced under conditions which approximate those in the field. The compounds, and some of their derivatives, inhibit the spore germination of a number of fungi in concentrations as low as 10−5 M. Inhibition is reversed by the addition of some divalent cations; this observation supports the identity of the hordatines with the natural defense agents of barley which have been demonstrated in earlier work.

The fungitoxicities of plant furocoumarins

SUMMARYA mixture of the furocoumarins pimpinellin, isopimpinellin, isobergapten and sphondin isolated from Heracleum sphondylium root was toxic to Gloeosporium limetticola, Botryis cinerea, Sclerotinia fructigena and Stereum purpureum at 200 p.p.m. or less in nutrient medium. The extractive of the leaves of plants that contain furocoumarins suppressed in vivo growth of G. limetticola and B. cinerea at concentrations lower than the contents of the extractive in the leaves. Furocoumarins may form an important class of natural defensive agents against fungi; this possibility is discussed.